In July 2015 a piece of debris from the missing Malaysia Airlines flight MH370 was discovered on Réunion, an island in the western Indian Ocean. Since then, more than 20 pieces of possible debris have been found on beaches, bringing to the forefront the subjects of ocean currents and ocean trash.

During the initial search for the plane, spotters reported on the amount of trash sighted in the Indian Ocean. The floating field of garbage there stretches for at least two million square miles. And that’s not the biggest garbage patch in our oceans. The largest buoyant garbage dump is in the Pacific Ocean. Those piles are formed by trash, plastic, discarded fishing gear, and debris from natural disasters (the 2011 Japanese tsunami, for example, sent tons of trash into the Pacific). Those patches pose a tremendous danger to the environment and to marine life.

There’s also the garbage in the ocean that you can’t see, the stuff below the surface that is just as much of a threat to marine life—if not a greater one—as the debris that’s visible on the surface.

The oceans are littered with what’s become known as “ghost fishing gear.” That refers to lost, abandoned, or discarded fishing implements—nets, traps, pots, lines—that are left in the ocean for one reason or another. According to the National Oceanic and Atmospheric Administration (NOAA) Marine Debris Program, some of the reasons gear goes ghost include: fishing during poor weather; conflicts with other fishing operations; gear getting snagged on obstructions on the seafloor (mountains, shipwrecks, etc.); gear overuse; and an excess of gear in play.

The idea of “ghost fishing gear” as an environmental concern is relatively recent. It was named in April of 1985. Each year 640,000 tons of ghost fishing gear is added to the litter in the oceans of the world. Ghost fishing gear wreaks havoc on marine animals and their environment. The most obvious concern is entanglement. Fish, seals, sea lions, turtles, dolphins, whales, seabirds, crustaceans—all are vulnerable to entanglement. If an animal doesn’t die from injuries sustained during the entanglement, it will suffocate or starve, trapped. A single net can take out an entire coral reef, killing some of the animals that live there and wiping out the habitat of many others, damaging an already sensitive ecosystem for years to come. Ghost fishing gear can also transport invasive species to new areas. And it can be ingested by marine animals, which can lead to injury and death.

Sometimes ghost fishing gear is released by accident. Law-abiding fishermen snag their nets on unknown obstructions and are forced to cut them loose. Bad weather hampers the retrieval of crab pots, shrimp pots, and lobster traps or snaps their surface lines. Commercial fisherman in the Pacific Northwest often pay more than $200 per trap, so they’re invested in not letting the trap turn into ghost gear because it’s not economically viable for them—in addition to the damage it causes to the ecosystem around them. But often derelict, worn, or damaged fishing gear is simply discarded by negligent fishers, who don’t know or don’t care about the impact that will have on the ocean and the animals that live there. Often there is no way to trace gear to specific fishing operations, and no one is held accountable.

Ghost fishing gear does not discriminate. The problems it causes are not limited to the gear’s targeted marine species. As of 2015, 136 different species of marine animals are known to have been tangled in ghost fishing gear. That number includes everything from fished-for fish, such as the Patagonian toothfish, to wholly unintended targets, such as seabirds.

A century ago fishing implements were made of less-stern stuff. That was good for the environment because when a net was lost, it degraded more readily than today’s durable plastic nylon and polypropylene, which can persist in the ocean for up to 600 years. Nets made of those synthetic materials will break up only when they float on the surface and are exposed to sunlight, which causes them to decay and eventually break into bits of plastic.

Those plastic bits are then ingested by marine life. Or they join the great floating garbage patches. National Geographic recently cited three studies showing that the world’s oceans hold 5.25 trillion pieces of plastic: some of it floats on the surface, but “some four billion plastic microfibers per square kilometer are suspended below.”

If they don’t float free and slowly decay, nets just keep on fishing, which isn’t good for animals, the environment, or even commercial fishing operations. World Animal Protection estimates that a single discarded fishing net that persists for 10 years can trap $20,000 worth of Dungeness crab. In a single year ghost fishing gear is responsible for the deaths of 136,000 large marine animals—whales, seals, and sea lions. The number for smaller marine life is not known, but it’s surely much, much greater.

Ghost fishing gear is uniquely poised to continue increasing in effectivity with its longevity. When gear traps a small fish, that fish in turn works like bait for a larger fish. And then that fish is trapped and attracts a still-larger fish. And so on until a multitude of different animals are trapped.

Gill Nets, Crab Pots, Long Lines, Oh MyGill nets are the worst offenders. Those types of nets have been outlawed in many places. The EU banned gill nets larger than 2.5 kilometers nearly 30 years ago. The UN banned them in international waters. Commercial operations using this type of net—which is essentially a drag-and-drop operation for the ocean—surely have targeted species. But the nets create floating walls, trapping everything in the vicinity.

Last December the Sea Shepherd organization—the same organization that was in the news recently for their dogged and successful pursuit of one of the most notorious poaching ships in the world—recovered a 25-kilometer-long gill net after it was abandoned by that same ship. When the Sea Shepherd crew hauled in the net, a job requiring the crew’s round-the-clock work for five straight days, they found—in addition to 200 dead fish of the targeted species, the Patagonian toothfish—rays, crabs, jellyfish, and other fish caught in the net. Most of those animals were also dead. It’s no coincidence that the type of net most likely to cause entanglements with marine life as ghost gear is the one used most frequently by poachers.

Crab pots, shrimp pots, and lobster traps are referred to as “passive” gear because they’re set and left unattended. Traps present twofold problems as ghost gear. There’s the potential for lost or discarded traps to continue to catch animals—everything from rockfish to sea lion pups—and then there’s the potential for entanglement in their float lines. Those lines lead up to buoys marking them on the surface. In many places traps are required to have biodegradable mesh panels on them so that after a certain amount of time, the panels will decay and render the traps useless. But it’s estimated that 250,000 crab pots are lost or discarded in the Gulf of Mexico every year, and many of them don’t conform to the required marine-animal safety regulations.

Long lines are less likely to kill marine life than other types of gear, but they’re not blameless. Long lines are lines with baited hooks, set either near the surface or the seafloor, depending on the targeted fish. They can stretch for miles. According to the NOAA, long lines near the surface are especially dangerous for seabirds, who are drawn to their bait. Turtles and whales can also be snagged on the hooks. Animals die from entanglement with the lines or suffer injury from the hooks.

Some SolutionsAs awareness of the very real environmental dangers of ghost fishing gear spreads, more organizations are taking action to combat these ecological hazards.

Off the coast of California, there is a sunken ship called the African Queen. Because of the location of the wreck—resting in a prime fishing spot—the boat functions as an invisible obstacle on the seafloor. Fishermen unaware of the boat often snag their gill nets on it. They leave the tangled nets behind. Until someone, like a volunteer from the Ocean Defenders Alliance, comes along and cleans them up.

Then there are organizations like Healthy Seas. That group comprises a nongovernmental organization and two businesses. They work to remove fishing nets from the oceans, saving the lives of countless marine animals in the process. Then the group goes a step further: recovered nets are shipped to Slovenia, where they are recycled into fibers for carpets and even clothing.

Hawaii, home to a hugely diverse population of rare and endangered marine life, has a lot to lose from ghost fishing gear. Because of its unique geographic location, Hawaii is often buffeted by lost, discarded fishing nets. A recent operation spent two years tracking an abandoned net off the coast of the northern Hawaiian Islands that weighed more than 11 tons. It killed turtles and sharks and countless smaller animals and fish. It also leveled a swath of coral reef. It took a team of divers and scientists days to carve it up for removal.

Hawaii’s Nets-to-Energy program was pioneered in 2002, and it has recycled more than 800 tons of ghost fishing nets since then. The government introduced a program to keep that gear out of landfills—it’s either incinerated or recycled. Discarded nets are taken to a recycler and chopped into bits. The bits are transported to a power plant in Honolulu, where they’re burned to create steam that powers a turbine. According to the NOAA, this has created enough energy to power “nearly 350 Hawai’i homes for a year.”

South Korea started working a decade ago to reduce marine debris. Their derelict gear buyback program, which pays fishermen between $4 and $20 for turning in a certain amount of a certain type of gear, collected nearly 30,000 tons of ghost gear in four years.

Those programs are pioneering solutions, and they are helping the environment and saving the lives of many marine animals in the process. But the fix for the ghost fishing gear problem lies in the prevention of its creation, in better tracking and identification technology to improve accountability and hold fishermen responsible for their gear and any damage it may cause marine life, and in better underwater GPS technology and topographic maps, which will help to reduce the frequency of collisions with objects on the seafloor, limiting the number of snagged nets that are set free to settle into floating graveyards.

Our new Britannica Explores newsletter has all the latest stories along with other great content.
Answering nagging questions like “Is zero an odd or even number?” and others!
Still curious? Sign up here to get Britannica Explores delivered right to your inbox!

Thank you for subscribing!

Be on the look out for the Britannica Explores newsletter to deliver more Demystified stories right to your inbox.